1. Field of the Invention
This invention relates to a coating composition and more particularly, to a coating composition comprising a blend of nitrocellulose and an ethylene/vinyl chloride/vinyl acetate copolymer.
2. Description of the Prior Art
Terpolymer resins prepared from ethylene, vinyl chloride and vinyl acetate are either available commercially or are disclosed in patent literature. For example, a terpolymer resin containing 25 percent by weight ethylene, 61 percent by weight vinyl chloride and 14 percent by weight vinyl acetate is sold commercially by Air Products and Chemicals, Inc. under the tradename Airflex 720 for paint application. This terpolymer is not compatible with nitrocellulose. A copolymer resin containing 60 percent by weight ethylene and 40 percent by weight vinyl acetate (Du Pont's Elvax 40) is compatible with nitrocellulose but due to its relatively high molecular weight, gives low solids at spray viscosity and has limited solubility in many lacquer solvents.
In U.S. Pat. No. 3,632,542 an emulsion polymerization process is disclosed for preparing a dispersion of ethylene, vinyl chloride and a vinyl ester, e.g., vinyl acetate. The contents of the dispersion is generally in the range of 5 to 25 percent by weight ethylene, 10 to 35 percent by weight vinyl chloride and 40 to 85 percent by weight vinyl ester. Such compositions when used as surface coating compositions give rise to films having improved resistance to hydrolysis by aqueous alkali.
The aforementioned commercial resins and dispersion do not have reduced flammability as well as other improved properties including reduced cost when blended with nitrocellulose.